Underwater is considered a silent place, the total opposite of The Little Mermaid, where fish and crabs sing about life “Under the Sea.” However, the Disney film might be a little closer to reality than we realize.
On land, nature is noisy. A walk through a forest would entertain a person with numerous bird calls that come together like a chirping and hooting choir. However, researchers have found that fish have a choir of their own. This underwater music emits from soloist fish that repeat the same calls, but when their calls overlap those of a different fish, they create a chorus.
“Under the Sea, Under the Sea”
Robert McCauley and his colleagues at Curtin University in Perth, Australia, have studied this intriguing ‘composition’ as reported in the International Journal of Animal Sound and its Recording. The research team has recorded species of vocal fish residing in the coastal waters near Port Hedland in Western Australia for about 18 months. They found seven unique fish choruses that took place at dawn and dusk. 
“Distinct diurnal patterns in the choruses were observed, associated with sunrise or sunset and in some cases, both,” the study reports. 
In these recordings, a wide variety of sounds can be heard to form a “song.” For example, the black-spotted croaker (Protonibea diacanthus) makes a low “foghorn” call, and a species or Terapontid has a low grunting call, while the quieter batfish makes a “ba-ba-ba” call as the third chorus.
“I’ve been listening to fish squawks, burble, and pops for nearly 30 years now, and they still amaze me with their variety,” says McCauley.
The Benefits of Fish Calls
Sound is a fundamental part of fish behaviors for their feeding needs, reproductions, and territorial fights. Nocturnal predators use their calls to stick together as they hunt, while fish awake during the day use their calls to defend their territory. Therefore, “You get the dusk and dawn choruses as you would with the birds in the forest,” says Steve Simpson, a marine biologist at the University of Exeter, UK.
Fish calls have a host of other benefits, such as helping baby crustaceans, corals, and other creatures find the reef where they will live since many species are born in open water and need to find their own home. 
A fish’s chorus can indicate a lot about it, including their location, their body size, the size of the group, their health status, and their behavioral patterns.
The recordings were made by a pair of sea-noise loggers. One was positioned near the shore of Port Hedland, and the second was placed 21.5 kilometers away in waters further offshore.
“This is a method that allows us to understand what’s happening at Port Hedland 24/7 for a year and a half,” says Simpson. “I don’t know any scuba diver that can stay down there that long!”
Listening to these calls help scientists monitor fish behaviors and their ecosystems, especially those harder to reach in low visibility waters.
“We are only just beginning to appreciate the complexity involved and still have only a crude idea of what is going on in the undersea acoustic environment,” says McCauley. 
Different Types of Fish “Songs”
Many species create sound by drumming their “sonic muscle” against their swim bladders. Others use stridulation, a rubbing technique that’s very similar to how crickets make their iconic calls. There’s also the hydrodynamic sound that occurs when creatures change directions as they swim.
These recordings are working to understand reef ecosystems by studying the complex behavior of their inhabitants.
Several of the same researchers posted another study in the ICES Journal of Marine Science about the nine chorus types found near the coast of Darwin Harbor, Australia.
“As we pick up more recording forms around Australia, we’ve been getting more and more data with choruses showing up throughout the day as well,” writes researcher Miles Parsons. “We also have sites where some of these choruses appear for a short time and then disappear, only to come back the next season/migration/whatever the driving cycle is.”
Future Research into Fish Choruses
Despite all of this research, our knowledge of fish choruses barely scratches the surface of the mysterious world of underwater life. We can affirm that the sounds are a sign of a healthy and diverse ecosystem, even though it sounds alien to us, and these signs are vital with all of the threats against reef habitats today, such as pollution, ocean acidification, warming water, and ship traffic. Fish choruses can be the key to conserving the reefs and the lives they sustain. 
If you’re curious for a more precise meaning of vibrant fish choruses, perhaps give “Under the Sea” from The Little Mermaid a listen (psst- that’s a joke, but I do really like that song).
 Miles J. G. Parsons, Chandra P. Salgado Kent, Angela Recalde-Salas, Robert D. McCauley. Fish choruses off Port Hedland, Western Australia. The International Journal of Animal Sound and its Recording. https://www.tandfonline.com/doi/full/10.1080/09524622.2016.1227940?ai=mv7m0 September 3, 2016
 Alexandra Sims. Under the sea: Fish recorded singing dawn choruses off Australia coast. Independent. https://www.independent.co.uk/news/science/fish-sing-dawn-chorus-audio-recording-australia-a7322346.html September 22, 2016
 Siel Ju. The sound of one coral reef growing. Mother NAture Network. https://www.mnn.com/earth-matters/animals/blogs/the-sound-of-one-coral-reef-growing May 17, 2010
 Greta Keenan. Fish recorded singing dawn chorus on reefs just like birds. New Scientist. https://www.newscientist.com/article/2106331-fish-recorded-singing-dawn-chorus-on-reefs-just-like-birds/ September 21, 2016
 Russell McLendon. Reef fish sing a ‘dawn chorus’ like songbirds. Mother NAture Network. https://www.mnn.com/earth-matters/animals/blogs/reef-fish-sing-dawn-chorus-birds September 22, 2016